Reduced particulate etching

ABSTRACT

A platen for use in a dry etching process for substrate production, the platen having a surface susceptible to chipping and/or particle generation from the dry etching process and a coating applied to at least a portion of the surface for rendering the surface less susceptible to chipping and/or particle generation, the coating comprising a silicon carbide coating

FIELD

This invention relates to the field of integrated circuit manufacturing.More particularly the invention relates to the treatment of platens forrendering them more useful in dry etching processes.

BACKGROUND

It is desirable to reduce extraneous particulate matter in theenvironments in which integrated circuits are processed. One reason forthis is that when airborne particles are deposited on the surface of thesubstrate on which the integrated circuits are formed, the particlestend to create processing defects in the integrated circuits, thusreducing the yield of the process and increasing the manufacturing costsof the integrated circuits.

One method by which particles are generated during processing is by thedegradation of a surface in a reaction chamber. For example, ceramicmaterials tend to be highly favored in certain types of reactionchambers because, among other things, they tolerate heat and tend to benon reactive in many environments. However, many ceramic materials tendto have relatively rough surfaces and relatively large pores which crackand spall relatively easily, thus creating particles. In some processes,where gases are distributed though the system, the particles thuscreated may become entrained in the flowing gases and redeposited on thesubstrates being process.

For example, dry etching is one method used to form integrated circuitson a substrate, such as a semiconductor substrate. In dry etchingprocesses, such as reactive ion etching, an etching gas is introduced bya gas distribution plate into an etching chamber containing thesubstrate. One problem encountered in such processes is chipping ordegradation of the gas distribution plate, which generate particulatesof the plate material. These particles from chipping or otherdegradation of the plate are carried by the etching gas to the substrateand tend to be detrimental to the integrity and quality of thesemiconductor substrate, as described above.

What is needed, therefore, is a system by which gas distribution platesare less susceptible to chipping and generation of particles so as toprovide gas distribution plates which are more suitable for theirintended purpose.

SUMMARY

The above and other needs are met by an improved platen for use in a dryetching process for substrate production. In a preferred embodiment,surfaces of the platen that are susceptible to chipping and particlegeneration from the dry etching process are coated with silicon carbideto render such surfaces less susceptible to chipping and particlegeneration. The coating is preferably applied to a thickness of at leastabout sixty microns by chemical vapor deposition.

It has been observed that the coating is particularly suitable forcoating ceramic silicon dioxide distribution plates. Such plates aredesirable from a cost basis, but are fragile and prone to chipping andparticle generation. By coating the plates in accordance with theinvention, the plate is rendered less prone to chipping and particlegeneration without unduly affecting the desirable cost attributes of theplates. Thus, the invention advantageously enables improved performancein an economical manner.

BRIEF DESCRIPTION OF THE DRAWING

Further advantages of the invention are apparent by reference to thedetailed description when considered in conjunction with the FIGURE,which is not to scale so as to more clearly show the details, and whichdepicts a platen according to the present invention.

DETAILED DESCRIPTION

With reference to FIG. 1, there is depicted a preferred embodiment of aplaten, such as gas distribution plate 10, in accordance with apreferred embodiment of the invention. The plate 10 preferably includesa base plate member 12 having a configuration suitable for distributinggas in a dry etching process, with a thickness defined between oppositesubstantially planar surfaces 14 and 16.

In a preferred embodiment, the base plate member 12 is made of ceramicsilicon carbide. Such plates are desirable in that they are relativelyinexpensive, but tend to be relatively fragile. Further, the surface ofplates formed from such ceramic materials tends to be rather rough,which roughness provides points that are relatively easily fracturedfrom the surface of the base 12, such as by thermal or mechanicalstresses. As a result, such plates tend to chip during the etchingprocess such that particles of the plate material are generated andcarried to the substrate during the etching process. This undesirablyaffects the etching process and may affect the quality of the substrate.

In accordance with the invention, it has been discovered thatsignificant reductions in the chipping of the plates and the generationof particles may be achieved by applying to at least a portion of theplate member 12, such as the surface 16, a coating 18. In a preferredembodiment, the coating 18 is a film of silicon carbide having athickness of at least about sixty microns. The silicon carbide materialfor the coating 18 is preferred, because it tends to be nonreactive tomany processes, such as dry etching processing. However, it isappreciated that other relatively nonreactive materials that arecompatible with the materials, processes, and intended functions asdescribed herein may also be used. It is understood that the coating 18may additionally applied to other surfaces of the plate member 12 suchas the surface 14 and the side edges of the plate 12.

A preferred method for coating the plate member 10 includes thefollowing steps. Most preferably, the edges of the base plate member 12are chamfered to reduce relatively sharp edges. In a cleaning step, theplate is first cleaned using an acid solution and ultrasonic treatment.A preferred acid solution is hydrofluoric acid, in a concentration offrom about five percent to about ten percent. After the cleaning step,the plate is dried in an oven, preferably at a temperature of from aboutone hundred centigrade to about two hundred centigrade, for a time offrom about six hours to about twelve hours. Next, the coating 18 isapplied, preferably as by chemical vapor deposition.

Application of the coating by chemical vapor deposition is particularlypreferred because the coating is applied in a highly conformal manner,and the coating is deposited as a relatively dense layer. Further, thesurface of the coating is preferably relatively smooth, and preferablydoes not have small cusps or other protrusions that would tend to easilybe chipped away from the surface of the coating and become airborne,such as in a process where a gas delivery system is used, and in aportion of the process reactor where such chips would tend to becomelofted in gases and swept through other portions of the reactor.Further, chemical vapor deposition tends to produce a film withrelatively large grains, which further tends to increase a depositedfilms resilience to chipping.

The chemical vapor deposited coating 18 tends to fill in any cracks thatare present in the base member 12, as well as generally seal the surfaceof the base member 12. Although a platen comprised entirely of avitreous material also tends to have reduced particulate generation,such platens are quite expensive. A platen 10 formed according to themethod as described herein provides the benefits of reduced particulategeneration and reduced cost of manufacture.

The thickness of the coating 18 is preferably selected, at least inpart, based upon the surface roughness or porosity of the base member12. For example, a surface 16 that is rougher or has larger pores ispreferably given a thicker coating of the sealing material 18, so as toencase all of the points of the rough surface and fill the pores of thebase member 12. On the other hand, a base member 12 with a smoothersurface and smaller pores, even though still fragile and prone tocracking, may preferably receive a thinner coating, which is sufficientto encase the points of the smoother surface and seal whatever cracksand pores may be present.

In a most preferred embodiment, the base member 12 is formed of ceramicsilicon carbide having a density of from about sixty percent to abouteighty percent, and the coating 18 has a density of at least aboutninety-nine percent.

The foregoing description of preferred embodiments for this inventionhave been presented for purposes of illustration and description. Theyare not intended to be exhaustive or to limit the invention to theprecise form disclosed. Obvious modifications or variations are possiblein light of the above teachings. The embodiments are chosen anddescribed in an effort to provide the best illustrations of theprinciples of the invention and its practical application, and tothereby enable one of ordinary skill in the art to utilize the inventionin various embodiments and with various modifications as is suited tothe particular use contemplated. All such modifications and variationsare within the scope of the invention as determined by the appendedclaims when interpreted in accordance with the breadth to which they arefairly, legally, and equitably entitled.

What is claimed is:
 1. A surface for use in a dry etching process, thesurface comprising: a silicon carbide base layer having a density ofbetween about sixty percent and about eighty percent, the base layerhaving chamfered edges, and a silicon carbide coating disposed on atleast a portion of an exposed surface of the silicon carbide base layer,the silicon carbide coating having a density of at least aboutninety-nine percent, and a thickness of about sixty microns, the siliconcarbide coating thereby sealing the exposed surface of the siliconcarbide base layer, and reducing particle generation from the siliconcarbide base layer during the dry etching process.